Green energy is to save energy on the premises of ensuring or and improving the lighting quality and efficiency; and to reduce the consumption of non-renewable resources and ecological and environmental pollutions. Not only green energy engineering aims at to improve the efficiency of lighting source, but also implement energy saving procedures throughout the lighting supply systems in order to improve energy-usage efficiency. Currently known lighting energy saving power supply devices available in the market are as follows:
1. Devices Based on Transformers
This kind of products currently dominates the market, and is popular in lighting energy saving improvement, and there are a few products available:                A. Electromagnetic self-coupled transformer fixed tap mechanical switch device: The device is cumbersome and incapable of voltage and luminance-regulation with load, it has fixed energy saving rate and is incapable of luminance-regulation.        B. Electromagnetic self-coupled transformer tap SCR switch device: the device is cumbersome, and it is of mutation type voltage and luminance-regulation, it may lead to the damages and lights-off on HID lamps, and it is incapable of accurate luminance-regulation, common-mode conduction exists during multiple SCR switch operation, which leads to high fault rate.        C. Electromagnetic self-coupled transformer step-less carbon brush switch device: the device is also cumbersome, and may generate electrical sparks during carbon brush sliding under heavy current, which leads to short service life and high fault rate.        D. Electromagnetic self-coupled transformer motor servo step-less carbon brush voltage and luminance-regulation device: it is cumbersome, and is of low efficient and high noise.        
2. SCR control device: The device may generate large input current harmonic wave and cause power system pollution; serious distortion on voltage output which causes EMI; only adaptive to inductive lighting load, not capable to meet the requirement of lighting diversification or industrial regulations.
3. Power-electronic power supply transformation devices: the devices achieve the AC power conversion by power-electronic devices, and it is of power supply optimization devices. The advantages of such devices are: adopting new technology, excellent output characteristics, light and handy, artificially intelligent, they represent a direction of developing energy saving systems.
However this kind of products available in the market now has several disadvantages: complicated topology, low-power capacity, poor reliability and efficiency, poor over-voltage resistance, small-range load adaptability (especially for inductive and capacitive load). Ability of resisting lightening strike, over-voltage and power surge is still a problem. Asymmetry of IGBT module structure leads to difficulty on power expansion and regional electrical stress.